A projection television is a type of television system for projecting and enlarging images by allowing three special cathode ray tubes to emit the three primary colors of red, green and blue, using a magnifying lens and a reflecting mirror. Although projection televisions utilize cathode ray tubes as do general television receivers, they utilize different methods for forming an image to display on a screen. In more detail, the general television cathode ray tube is limited in its screen size. Thus, not only does the fabrication of large-sized cathode ray tubes present several technical problems, but also the inherent bulk and weight resulting from the enlargement acts as a limiting factor in their production. Therefore, the projection television comes to the forefront as a means capable of obtaining a large-sized screen while solving the above-described problems. In projection televisions, the cathode ray tube itself functions as the electron gun of the general television cathode ray tube, and light radiating from the cathode ray tube passes through a projection lens via a color-selective mirror. Thereafter, the light reflected by means of a reflecting mirror finally forms an image on a large-sized screen separated from the cathode ray tube. This is the typical principle of the projection TV.
However, in such projection televisions, considerable heat is generated in the panel of the cathode ray tube, which raises the problem of dealing with the generated heat. Due to this fact, a liquid coolant coupling apparatus containing a liquid coolant, which is a kind of a radiator, is installed in the front of the panel. One example of the liquid coolant coupling apparatus is illustrated in FIG. 1 whose explicit construction will be described below.
FIG. 1 is a schematic side view of a conventional liquid coolant coupling apparatus in a projection cathode ray tube, and FIG. 2 is a plan view thereof. As illustrated in FIGS. 1 and 2, an anode cap 2 supplied with a high voltage is formed on the side of a cathode ray tube 1. A gripping plate 5 which is for pressing so as to fix cathode ray tube 1 to a radiating plate 6 by screwing four bolts 3 is fixed to the front of cathode ray tube 1. Each bolt 3 has a spring 4 for fine adjustment of the screw pressure.
As shown in FIG. 2, gripping plate 5 constituted as one body has a hole of a predetermined size formed in its center to allow the neck end of cathode ray tube 1 to be inserted therein. Also, four through holes for respective clamping bolts 3 are formed near the perimeter of gripping plate 5.
However, the conventional liquid coolant coupling apparatus constructed as above is disadvantageous in that the unavoidable approach of gripping plate 5 upon anode cap 2 and thus upon the anode leads to a risk of arcing as a high voltage is applied to the anode. Furthermore, the centering of cathode ray tube 1 and radiating plate 6 is difficult during their coupling, and the coupling apparatus is unnecessarily bulky and heavy.